The medium and heavy duty truck manufacturing industry manufactures certain vehicles as cab chassis type vehicles. A cab chassis allows aftermarket installation of equipment which is specific to a particular vocational use of the vehicle.
Cab chassis vehicles which are to be used in certain vocations have especially long lengths and therefore comprise especially long chassis frames. When such a vehicle is parked for vocational use, various forces and/or torques may be exerted on the chassis frame, and may tend to bend and/or twist the frame. Extreme forces and/or torques exceeding design specification may even cause permanent frame deformation.
It has been a practice in the industry for an aftermarket manufacturer of certain vocational equipment which is to be installed on a cab chassis to provide that equipment with a sub-base which is intended to rigidify the chassis frame.